Organic light-emitting devices (OLEDs) are regarded as the third-generation display technology, because they have advantages such as active light-emission, good temperature characteristics, low power consumption, fast response, flexibility, ultra-thin and low costs.
According to light-emission directions, an OLED can be divided into three types: bottom-emission OLED, top-emission OLED, and double-emission OLED. A bottom-emission OLED refers to an OLED with light emission from a substrate; a double-emission OLED refers to an OLED with light emission from both a substrate and the top of the device; a top-emission OLED refers to an OLED with light emission from the top of the device. Because it does not affect a top-emission OLED whether or not a substrate is light-transmitting, the aperture ratio of a display panel can be effectively improved, the design of a TFT circuit on a substrate can be expanded, and the choices of electrode materials can be widened; furthermore, the integration of the device with a TFT circuit can be facilitated. An OLED is very sensitive to moisture and oxygen, and therefore moisture and oxygen that penetrates into the inside of the OLED will corrode the organic functional layer and the electrode material, which severely affects the service-life of the device. Therefore, in order to prolong device's service-life and improve device's stability, it is necessary to have an OLED subjected to an encapsulating treatment to form an OLED encapsulating structure, for example, a barrier layer may be formed on the OLED, and the barrier layer may comprise an inorganic insulating layer and an organic insulating layer, so as to prevent moisture and oxygen from penetration into the OLED.
A top-emission OLED can improve device's efficiency, narrow spectrums and improve color-purity, but often suffers micro-cavity effect. Micro-cavity effect will cause the light-emitting spectra of an OLED to change along with the viewing angle, which results in that a viewing-angle dependence problem occurs to the OLED.